1. Field of the Invention
The present invention generally relates to a device for storing and supplying an active liquid in an ink jet printhead and, more particularly, to a device for storing and supplying an active liquid in an ink jet printhead wherein a heating chamber is heated to change the shape of the membrane that separates an ink chamber storing the active liquid from the heating chamber and thereby the ink disposed in an ink chamber is jetted onto a print media.
2. Discussion of Related Art
Generally, an ink jet printer has a control section which is receptive to print data generated from a system. The control section processes the print data, generating a control signal for driving an ink jet printhead to jet ink stored therein through a nozzle in order to produce an image onto the media in response to the print data.
An exemplary ink jet printhead stores and jets ink in drops in response to the control signal applied from the control section. The exemplary ink jet printhead is includes: an elastic body for storing ink; a housing having the ink-storing elastic body built therein, and forming an ink filter which filters the ink and is glued to the bottom surface of the ink-storing elastic body, an ink stand pipe which forms a feeding path of the ink filtered through the ink filter, and an ink via; an ink injector for injecting the ink supplied through the ink via of the housing in drops in response to an electrical signal applied to an electrical connection; and a housing cover for covering the housing tightly by heat or ultrasonic fusion after the ink-storing elastic body is mounted in the housing, and making an orifice to maintain the atmospheric pressure constant.
The ink enjector of the exemplary inkjet printhead includes: a substrate providing a support; a metal layer deposited on the substrate; a heater deposited on the metal layer in a specified pattern to convert electrical energy to heat; two electrodes deposited in contact with the heater in order to supply electrical energy to the heater; a heating chamber barrier deposited on the upper surface of the two electrodes so as to form a heating chamber; plural membranes glued to the upper surface of the heating chamber barrier and heated by the heater to be expanded and changed in shape; an ink chamber barrier glued to the upper surface of the plural membranes so as to form an ink chamber; and a nozzle plate glued to form an orifice in accord to the ink chamber.
The ink jet printhead of such a configuration maintains the pressure in the housing at the atmospheric pressure through the orifice disposed at a specified position in the housing cover. Jetting ink through the ink injector while maintaining the pressure in the housing at the atmospheric pressure causes a suction, that is, a buoyant pressure generated from the jetting force.
The buoyant pressure produced in the ink enjector of the ink jet printhead forces the ink in an open shell formed in the ink-storing elastic body to be filtered through the ink filter and supplied to the ink enjector via the ink stand pipe and ink via.
The ink supplied to the ink enjector forms droplets and is jetted according to the electrical signal applied to the electrical connection. That is, electrical energy is applied to the heater through the two electrodes, wherein the heater is deposited in a specified pattern on the metal layer overlying the substrate which is to support the ink enjector.
The electrical energy applied to the heater heats the active liquid filled in the heating chamber to create the vapor pressure, which causes a plurality of membranes to be expanded.
In addition to the expansion of the plural membranes, the vapor pressure expands the ink which is supplied to the ink chamber defined by the ink via and the ink chamber barrier. As the expansion of ink interrupts the electrical energy supply to the two electrodes, the expanded ink forms droplets due to the surface tension and is jetted onto the print media.
Once the ink droplets are jetted through the ink enjector, external air is introduced through the orifice disposed at a specified position in the housing cover such that the top portion of the ink-storing elastic body is filled with air in an amount as much as the jetted ink. Under pressure as much as the amount of air that fills the top portion of the ink-storing elastic body, the ink moves down to the bottom of the elastic body.
The ink enjector jets the ink onto the print media to produce a font or graphic image according to the electrical signal applied from the electrical connection.
It is, however, difficult to check the complete enjection of the active liquid into the respective heating chambers disposed in the ink enjector of the ink jet printhead utilizing membranes. Also, the enjector is inapplicable to long time use in that the active liquid within the ink injector is heated to vaporization or consumption, resulting in deterioration of the injection rate of the ink with a consequence of dot omission. Furthermore, as the ink chamber is formed with the active ink jetted thereinto, the formation of the ink chamber is difficult in the exemplary art.
U.S. Pat. No. 4,364,059 to Nagayama, entitled Ink Jet Printing Apparatus, discloses an ink jet printing apparatus whereby ink is recirculated from a reservoir through an ink ejection head and back to the reservoir while it has been heated prior to actual printing to purge air from the ink and prevent erroneous ejection. U.S. Pat. No. 4,580,148 to Domoto et al., entitled Thermal Ink Jet Printer With Droplet Ejection By Bubble Collapse, discloses a thermal ink jet printer with droplet ejection by bubble collapse, whereby a thermal ink jet printhead ejects ink droplets on demand by utilizing the conservation of momentum of collapsing bubbles in a layer of liquid ink having a predetermined thickness. It is disclosed that the printhead has an ink containing chamber with an array of individually addressable heating elements on one chamber interior surface which are aligned with an elongated opening in a parallel, confronting chamber wall. U.S. Pat. No. 4,788,556 to Hoisington et al., entitled Deaeration Of Ink In An Ink Jet System, discloses a deaeration of ink in an ink jet system, whereby an elongated ink path leading to an ink jet head is formed between two permeable membranes. The membranes are disclosed as being backed by air plenums which contain support members to hold the membranes in position. Reduced pressure is disclosed as being applied to the plenums to extract dissolved air from the ink in the ink path, and increased pressure can also be applied to the plenums to eject ink from the inkjet head for purging. It is disclosed that within the ink jet head ink is circulated convectively from the orifice to the deaerating path even when the jet is not jetting ink.
U.S. Pat. No. 5,084,713 to Wong, entitled Method And Apparatus For Cooling Thermal Ink Jet Print Heads discloses a method and apparatus for cooling thermal ink jet printheads. A thermal ink jet cartridge is disclosed which uses a resistor assembly to eject ink from the cartridge. To control heat generated by the resistors, a cooling system is disclosed as being provided that consists of an ink channel positioned adjacent the resistor substrate, with the channel being supplied with ink from a chamber within the cartridge. The ink flowing through the channel contacts the substrate, causing a cooling effect, the ink then being returned to the chamber in the cartridge. It is disclosed that the system may consist of a thin-film resistor positioned adjacent at least one of the openings provided between the channel and the chamber, and when the resistor is energized and heated, it is disclosed as causing ink to flow through the openings and back into the chamber. U.S. Pat. No. 5,017,941 to Drake, entitled Thermal Ink Jet Printhead With Recirculating Cooling System, discloses a thermal ink jet printhead with recirculating cooling system, whereby a thermal ink jet printer is disclosed as having a printhead with a passageway therein for the circulation of a cooling fluid therethrough, with the passageway being parallel and closely adjacent the array of bubble generating heating elements. The printhead is disclosed as being composed of mated silicon channel and heater plates, with the passageway being formed in an embodiment by forming a groove in the heater plate surface opposite the one containing the heating elements and addressing electrodes followed by the mating of a silicon sealing plate having inlet and outlet openings etched therein. Tubes for circulating a cooling fluid, such as ink, are disclosed and are sealingly attached to the inlet and outlet openings. In another embodiment, it is disclosed that the groove may be formed in the sealing plate or in both the sealing plate and the printhead heater plate. In a further embodiment, it is disclosed the passageway for the cooling fluid is provided by etching a channel in a thick film layer deposited on the heater plate surface opposite the one with the heating elements. It is disclosed that the circulated cooling fluid prevents printhead temperature fluctuations during the printing operation.
U.S. Pat. No. 5,265,315 to Hoisington et al., entitled Method Of Making A Thin-Film Transducer Ink Jet Head discloses a method of making a thin-film transducer ink jet head, by oxidizing one surface of a silicon wafer to provide a dielectric layer, forming electrodes on the layer by photoresist processing techniques, depositing one or more layers of PZT material to provide a thin-film piezoelectric layer, forming another pattern of electrodes on the surface of the PZT layer by photoresist techniques, and selectively etching the silicon substrate in the region of the electrodes to provide an ink chamber. Thereafter, an orifice plate is disclosed as being affixed to the substrate to enclose the ink chambers and provide an ink orifice for each of the chambers. U.S. Pat. No. 5,231,424 to Kaneko et al., entitled Ink Jet Recording Apparatus With Efficient Circulation Recovery, discloses ink jet recording apparatus with circulation recovery. The ink jet recording apparatus is disclosed as including a recording head for recording on the recording medium by discharging ink through discharge ports, an ink tank for storing the ink, a first ink flow channel for passing the ink from the ink tank to the recording head, a second ink flow channel for passing the ink from the recording head into the ink tank, a filter provided in the first ink flow channel, and a back flow prevention valve provided in the second ink flow channel.
U.S. Pat. No. 5,119,115 to Buat et al., entitled Thermal Ink Jet Print Head With Removable Ink Cartridge, discloses a thermal ink jet printhead with a removable ink cartridge, whereby in a thermal ink jet printhead the ink is expelled in the form of small drops through a plurality of nozzles communicating with corresponding expulsion chambers for expulsion of the ink through the effect of rapid heating of heater elements contained in the expulsion chambers. It is disclosed that the nozzles, the expulsion chambers, the heater elements and the associated electrical conductors are constructed in a plurality of metal layers and insulating layers supported by a silicon plate with the plate being fixed to the structure of the head and being supplied with ink contained in a movable cartridge fitted to the structure of the head. U.S. Pat. No. 5,659,346 to Moynihan et al., entitled Simplified Ink Jet Head, discloses a simplified ink jet head, whereby a carbon plate is disclosed as being formed with orifice passages extending through the plate, pressure chambers on one side of the plate, flow-through passages on the other side of the plate and ink supply passages, and a piezoelectric plate having a conductive coating on the exposed side is disclosed as being affixed to the pressure chamber side of the carbon plate by a thin layer of epoxy adhesive, with the conductive coating on the piezoelectric plate being photo-etched to produce an electrode pattern corresponding to the pattern of the pressure chambers in the carbon plate, and an orifice plate is disclosed as being affixed by a thin layer of epoxy adhesive to the opposite surface of the carbon plate with orifices aligned with the orifice passages in the carbon plate. It is disclosed that since the carbon plate is conductive, it can be used as an electrode on the opposite side of the piezoelectric plate, and it is disclosed that it can provide a communication path between a vacuum source and an air-permeable, ink-impermeable layer on the ink passages to remove dissolved air from the ink in the passages.